Rotorcraft and method of controlling rotorcraft

ABSTRACT

According to one implementation, a rotorcraft includes a first rotorcraft and at least one second rotorcraft. The first rotorcraft has a first main rotor and a first tail rotor. The at least one second rotorcraft has a second main rotor and a second tail rotor. The at least one second rotorcraft are attachable and detachable to and from the first rotorcraft. Further, according to one implementation, a method of controlling the above-mentioned rotorcraft includes: flying the first rotorcraft, to which the at least one second rotorcraft has been attached, to a destination; and separating the at least one second rotorcraft from the first rotorcraft at the destination.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2018-211862, filed on Nov. 12, 2018; the entire contents of which are incorporated herein by reference.

FIELD

Implementations described herein relate generally to a rotorcraft and a method of controlling a rotorcraft.

BACKGROUND

Conventionally, a multicopter which can house slave rotorcrafts has been suggested as a rotorcraft which can carry out missions at a plurality of loci simultaneously (for example, refer to Japanese Patent Application Publication JP2016-064768 A). A multicopter is a kind of a helicopter and a rotorcraft which has not less than three rotors.

Moreover, a method of remotely controlling an unmanned aircraft, which functions as a slave rotorcraft, by another unmanned aircraft, which functions as a master rotorcraft, through wireless communication has also been suggested (for example, refer to Japanese Patent Application Publication JP2015-191254 A).

An object of the present invention is to provide a rotorcraft and a method of controlling a rotorcraft which can carry out missions at loci simultaneously with an easier maneuvering.

SUMMARY OF THE INVENTION

In general, according to one implementation, a rotorcraft includes a first rotorcraft and at least one second rotorcraft. The first rotorcraft has a first main rotor and a first tail rotor. The at least one second rotorcraft has a second main rotor and a second tail rotor. The at least one second rotorcraft are attachable and detachable to and from the first rotorcraft.

Further, according to one implementation, a method of controlling the above-mentioned rotorcraft includes: flying the first rotorcraft, to which the at least one second rotorcraft has been attached, to a destination; and separating the at least one second rotorcraft from the first rotorcraft at the destination.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a perspective view showing a structure of a rotorcraft according to an implementation of the present invention;

FIG. 2 shows the first specific example of the detachable structure shown in FIG. 1;

FIG. 3 shows the second specific example of the detachable structure shown in FIG. 1;

FIG. 4 is an enlarged longitudinal sectional view showing the third specific example of the detachable structure shown in FIG. 1;

FIG. 5 is an enlarged longitudinal sectional view showing the docked detachable structure shown in FIG. 4;

FIG. 6 shows an example of structure for supplying an electric power to the battery in each of the slave rotorcrafts from the master rotorcraft shown in FIG. 1;

FIG. 7 shows a state where the slave rotorcraft has been docked with the detachable arms of the master rotorcraft shown in FIG. 6;

FIG. 8 is a top view showing an example where the slave rotorcrafts of the rotorcraft shown in FIG. 1 have been connected to the master rotorcraft at different positions respectively;

FIG. 9 shows an example in which each of the slave rotorcrafts shown in FIG. 1 can be tilted relative to the master rotorcraft; and

FIG. 10 shows an example in which the second main rotor 3A of each of the slave rotorcrafts 3 shown in FIG. 1 can be tilted relative to the slave rotorcraft 3.

DETAILED DESCRIPTION

A rotorcraft and a method of controlling a rotorcraft according to implementations of the present invention will be described with reference to the accompanying drawings.

(Structure and Function of Rotorcraft)

FIG. 1 is a perspective view showing a structure of a rotorcraft according to an implementation of the present invention.

A rotorcraft 1 has a master rotorcraft 2 and one or more slave rotorcrafts 3 which can be attached to and detached from the master rotorcraft 2. Although FIG. 1 shows an example in which the four slave rotorcrafts 3 are coupled to the master rotorcraft 2, the number of the slave rotorcrafts 3 is flexible.

The master rotorcraft 2 is the first rotorcraft which has the first main rotor 2A and the first tail rotor 2B. That is, the master rotorcraft 2 can fly as the independent first rotorcraft regardless of whether the slave rotorcrafts 3 have been coupled to the master rotorcraft 2. Although the first tail rotor 2B is a ducted fan surrounded by an annular duct in an example shown in FIG. 1, the first tail rotor 2B may have another structure.

On the other hand, each of the slave rotorcrafts 3 is the second rotorcraft which has the second main rotor 3A and the second tail rotor 3B. That is, each of the slave rotorcrafts 3 can fly as the independent second rotorcraft even when the slave rotorcraft 3 has not been coupled to the master rotorcraft 2.

Each of the master rotorcraft 2 and the slave rotorcraft 3 may be a manned aircraft or an unmanned aircraft. Whether the master rotorcraft 2 and the slave rotorcrafts 3 are manned aircrafts or unmanned aircrafts respectively can be determined according to respective missions of the master rotorcrafts 2 and the slave rotorcrafts 3, and/or needs of a user. When both of the master rotorcraft 2 and the slave rotorcrafts 3 are unmanned aircrafts, there is an advantage that no pilot is necessary, which leads to improvement in safety particularly in a case of a defensive purpose.

Examples of missions of the master rotorcraft 2 and the slave rotorcraft 3 include a checkup of an infrastructure, such as a road, a railroad, a water and sewerage, a power transmission network, a port, a dam and a communication facility, as well as transmission of voices or radio waves for broadcasting, photographing from the sky and a defensive mission. Examples of a defensive mission include a mission to load explosives on a part or all of the master rotorcraft 2 and the slave rotorcrafts 3 to explode the explosives at a target area as well as a mission to fly as many targets.

When each of the master rotorcraft 2 and the slave rotorcrafts 3 is an unmanned aircraft, the master rotorcraft 2 and each slave rotorcraft 3 can be maneuvered at a remote place by wirelessly transmitting control signals from a controller 4 having a wireless device 4A to a control system 5A and a control system 5B respectively mounted on the master rotorcraft 2 and each of the slave rotorcrafts 3 as exemplified by FIG. 1. Alternatively, the master rotorcraft 2 and each slave rotorcraft 3 may fly on automatic pilot by previously installing flight programs in the control system 5A and the control system 5B mounted on the master rotorcraft 2 and each slave rotorcraft 3 respectively.

Each of the first main rotor 2A, the first tail rotor 2B, the second main rotors 3A and the second tail rotors 3B of the master rotorcraft 2 and the slave rotorcrafts 3 can be rotated by an engines 6, such as a reciprocating engine or a gas turbine engine, or a motor 7. Alternatively, each of the first main rotor 2A, the first tail rotor 2B, the second main rotors 3A and the second tail rotors 3B of the master rotorcraft 2 and the slave rotorcrafts 3 may be rotated by both the engine 6 and the motor 7. As a practical example, the motors 7 may be rotated by the power of the engine 6 while the rotors may be rotated by the motors 7 respectively.

In general, the larger size a rotorcraft has, the larger power it becomes necessary to mount an engine having a necessary scale in order to generate. On the contrary, the smaller size a rotorcraft has, the more frequently an electric type of rotorcraft of which maintenance is easy is adopted.

Accordingly, it is practical that the master rotorcraft 2 to which the slave rotorcrafts 3 are coupled is a large-sized rotorcraft whose the first main rotor 2A and the first tail rotor 2B are rotated by the engine 6 as exemplified in FIG. 1. As a matter of course, the first main rotor 2A and the first tail rotor 2B may be rotated by the motors 7 rotated by the engine 6 as mentioned above.

On the contrary, it is practical that each of the slave rotorcrafts 3 is a small-sized rotorcraft, having the electric second main rotor 3A and the electric second tail rotor 3B each rotating only by the motor 7, without the engine 6.

In this case, a battery 8 for rotating the second main rotor 3A and the second tail rotor 3B by supplying an electric power to the motor 7 is mounted on each of the slave rotorcrafts 3. Thus, at least one of a battery charger 9 and a generator 10 for charging the batteries 8 of the slave rotorcrafts 3 in a state where the slave rotorcrafts 3 has been coupled to the master rotorcraft 2 can be mounted in the master rotorcraft 2.

As a practical example, both of the battery charger 9, composed of a battery, and the generator 10, which generates an electric power by the power of the engine 6, can be mounted in the master rotorcraft 2 as shown in FIG. 1. In this case, the batteries 8 of the slave rotorcrafts 3 can be charged with an electric power generated by the generator 10 while a surplus electric power can be supplied to the battery charger 9. Then, when an electric power has been charged in the battery charger 9, the batteries 8 of the slave rotorcrafts 3 can be charged also with an electric power charged in the battery charger 9.

Each of the slave rotorcrafts 3 to be charged is coupled to the master rotorcraft 2 by a detachable structure 11. Therefore, it is necessary to charge the battery 8 of each slave rotorcraft 3 through the detachable structure 11. Accordingly, a charging method can be determined according to the detachable structure 11.

In an example shown in FIG. 1, the detachable structure 11 has a detachable arm 11A and each of the slave rotorcrafts 3 has been configured so that the slave rotorcraft 3 can be separated and coupled from and to the master rotorcraft 2 even during a flight as well as during landing. A method of attaching and detaching each slave rotorcraft 3 to and from the detachable arm 11A of the master rotorcraft 2 is flexible.

FIG. 2 shows the first specific example of the detachable structure 11 shown in FIG. 1.

As a specific example, at least one of an electromagnet 20A and an electromagnet 20B can be attached to at least one of the master rotorcraft 2 and the slave rotorcraft 3 so that generations of magnetic forces of the electromagnet 20A and the electromagnet 20B can be controlled by the control system 5A and the control system 5B respectively as shown in FIG. 2. Then, the slave rotorcraft 3 can be attached to and detached from the master rotorcraft 2 by supplying control signals from the control system 5A and the control system 5B to the electromagnet 20A and the electromagnet 20B to switch magnetic forces between the on states and the off states respectively.

FIG. 3 shows the second specific example of the detachable structure 11 shown in FIG. 1.

As another specific example, a hand 30 which opens and closes by the control system 5A can be attached on the tip of the detachable arm 11A in the master rotorcraft 2 side while a coupling shaft 31 can be attached to the slave rotorcraft 3 as shown in FIG. 3. Thus, a coupling structure in which the hand 30 in the master rotorcraft 2 side holds the coupling shaft 31 in the slave rotorcraft 3 side may be adopted as the detachable structure 11. In this case, the slave rotorcraft 3 can be attached to and detached from the master rotorcraft 2 by controlling the opening and closing of the hand 30.

FIG. 4 is an enlarged longitudinal sectional view showing the third specific example of the detachable structure 11 shown in FIG. 1, and FIG. 5 is an enlarged longitudinal sectional view showing the docked detachable structure 11 shown in FIG. 4.

As yet another specific example, the detachable structure 11 may also be composed by a motor 40, a ball screw 41, springs 42, rotating shafts 43, stoppers 44, a female screw 45 and a projection 47 having a groove 46 as shown in FIG. 4. Specifically, the ball screw 41, rotated by the motor 40, and the stoppers 44, rotating around the rotating shafts 43 by expansion and contraction of the springs 42 respectively, are attached to the tip of the detachable arm 11A in the master rotorcraft 2 side. Meanwhile, the female screw 45 and the projection 47 having the groove 46 for fitting the stoppers 44 are formed in the slave rotorcraft 3. The tip of the detachable arm 11A in the master rotorcraft 2 side has a concave portion 48 which fits with the projection 47 of the slave rotorcraft 3. The tip of the ball screw 41 and the front end or the rear end of each stopper 44 are projected inside the concave portion 48. The number of the stoppers 44 is flexible. For example, about two to four stoppers 44 can be placed at a same interval along a circle whose center is the rotation axis of the ball screw 41.

In a case of the detachable structure 11 having a structure exemplified in FIG. 4, driving the motor 40 to fasten the ball screw 41 in the master rotorcraft 2 side to the female screw 45 in the slave rotorcraft 3 side makes it possible to pull the projection 47 in the slave rotorcraft 3 side toward the concave portion 48 formed on the detachable arm 11A in the master rotorcraft 2 side.

Each stopper 44 has a convex portion 44A at the rear end. The convex portion 44A is projected to the concave portion 48 by the elastic force of the spring 42 as exemplified in FIG. 4 when the projection 47 of the slave rotorcraft 3 has not been inserted in the concave portion 48 at the end part of the detachable arm 11A. Meanwhile, when the projection 47 of the slave rotorcraft 3 is inserted in the concave portion 48 at the end part of the detachable arm 11A, the respective springs 42 contract since the end part of the projection 47 of the slave rotorcraft 3 is pressed against the respective convex portions 44A formed at the rear ends of the stoppers 44 as exemplified in FIG. 5. As a result, the stoppers 44 respectively rotate around the rotating shafts 43 so that convex portions 44B formed at the end parts of the stoppers 44 project into the concave portion 48. The convex portions 44B, at the end parts of the stoppers 44, which have projected inside the concave portion 48, respectively fit the groove 46 formed on the projection 47 of the slave rotorcraft 3. Thereby, the slave rotorcraft 3 can be held by the detachable arm 11A of the master rotorcraft 2.

Note that, a typical rotorcraft has stub wings (small wings) 47A as exemplified in FIG. 4 and FIG. 5. The stub wings 47A are short wings projecting to the right and left side of the fuselage. Accordingly, when the slave rotorcraft 3 has the stub wings 47A, at least one of the stub wings 47A can be used as the projection 47 inserted into the concave portion 48 in the master rotorcraft 2 side. Similarly, the electromagnet 20B exemplified in FIG. 2 or the coupling shaft 31 exemplified in FIG. 3 may also be attached to at least one of the stub wings 47A of the slave rotorcraft 3.

In the state where the slave rotorcraft 3 has been docked with the master rotorcraft 2T, the battery 8 of the slave rotorcraft 3 can be charged by the battery charger 9 and the generator 10 of the master rotorcraft 2 as mentioned above. When the battery 8 of the slave rotorcraft 3 is charged by the battery charger 9 and the generator 10 of the master rotorcraft 2, a charging method according to a structure of the detachable structure 11 can be adopted. Concrete examples of a method of charging the battery 8 of the slave rotorcraft 3 by the battery charger 9 and the generator 10 of the master rotorcraft 2 through the detachable structure 11 include a wireless power feeding in addition to a power feeding method by using a slip ring or the like to form electric contact points on both the master rotorcraft 2 and the slave rotorcraft 3 so that the electric contact points can be mechanically contacted with each other for the power feeding. When the battery 8 of the slave rotorcraft 3 is charged by a wireless power feeding, wireless devices for the wireless power feeding are prepared in the master rotorcraft 2 and the slave rotorcraft 3 respectively.

FIG. 6 shows an example of structure for supplying an electric power to the battery 8 in each of the slave rotorcrafts 3 from the master rotorcraft 2 shown in FIG. 1 while FIG. 7 shows a state where the slave rotorcraft 3 has been docked with the detachable arms 11A of the master rotorcraft 2 shown in FIG. 6.

When the slave rotorcraft 3 has the projections 47, such as the stub wings 47A, the concave portion 48 which fits the projection 47 of the slave rotorcraft 3 can be formed at the end part of the detachable arm 11A of the master rotorcraft 2, as exemplified in FIG. 6, similarly to an example shown in FIG. 4 and FIG. 5. Then, at least one pair of an electric supply port 50A and an electric supply port 50B for supplying electric power can be prepared on the concave portion 48 formed at the end part of the detachable arm 11A of the master rotorcraft 2 and the projection 47 of the slave rotorcraft 3.

More specifically, mechanical contact points serving as at least one pair of the electric supply port 50A and the electric supply port 50B can be disposed on the concave portion 48 formed at the end part of the detachable arm 11A of the master rotorcraft 2 and the projection 47 of the slave rotorcraft 3 so that the mechanical contact points may contact with each other in the state where the slave rotorcraft 3 has been docked with the master rotorcraft 2 by inserting the projection 47 in the concave portion 48 as exemplified in FIG. 7. Alternatively, at least one pair of the non-contact electric supply port 50A and the non-contact electric supply port 50B for feeding power wirelessly may be disposed on the projection 47 of the slave rotorcraft 3 and the concave portion 48 formed at the end part of the detachable arm 11A of the master rotorcraft 2.

It is appropriate to apply waterproof treatment to each electric supply port 50A and each electric supply port 50B since each electric supply port 50A, disposed on the concave portion 48, and each electric supply port 50B, disposed on the projection 47, are exposed to the weather while the slave rotorcraft 3 has been separated from the master rotorcraft 2.

Each of the stub wings 47A of the slave rotorcraft 3 may have a tilt function. In that case, a harness 52 for feeding power can be disposed inside a rotation shaft 51 of at least one of the stub wings 47A, for tilting the stub wing 47A, as exemplified in FIG. 6 and FIG. 7. Alternatively, power may be supplied wirelessly between the stub wing 47A and the fuselage of the slave rotorcraft 3. Thereby, even when the stub wings 47A are tilted, interference of the stub wing 47A with the harness 52 can be avoided. In other words, at least one electric supply port 50B can be disposed at the end part of the stub wing 47A having a tilt function.

When each of the master rotorcraft 2 and the slave rotorcrafts 3 is an unmanned aircraft, not only maneuvering of the master rotorcraft 2 and the slave rotorcrafts 3, but also attachment and detachment of each slave rotorcraft 3 to and from the master rotorcraft 2 in addition to charging the batteries 8 of the slave rotorcrafts 3 can be performed by remote controls with wireless transmissions of control signals from the controller 4 to the control system 5A of the master rotorcraft 2 and the control systems 5B of the slave rotorcrafts 3, or automatically controlled by flight programs previously stored in the control system 5A of the master rotorcraft 2 and the control systems 5B of the slave rotorcrafts 3.

As a matter of course, when only the master rotorcraft 2 is a manned aircraft, a pilot of the master rotorcraft 2 can attach and detach each of the slave rotorcrafts 3 to and from the master rotorcraft 2, and charge the batteries 8 of the slave rotorcrafts 3, by manual operations of the control system 5A of the master rotorcraft 2 and the control systems 5B of the slave rotorcrafts 3. Meanwhile, when at least one of the slave rotorcrafts 3 is a manned aircraft, a pilot of the slave rotorcraft 3 side can attach and detach each of the slave rotorcrafts 3 to and from the master rotorcraft 2, and charge the batteries 8 of the slave rotorcrafts 3, by manual operations of the control system 5A of the master rotorcraft 2 and the control systems 5B of the slave rotorcrafts 3.

On the contrary, even when at least one of the master rotorcraft 2 and the slave rotorcrafts 3 is a manned aircraft, each of the slave rotorcrafts 3 can be attached and detached to and from the master rotorcraft 2 while the batteries 8 of the slave rotorcrafts 3 can be charged, by remote operations with wireless transmissions of control signals from the controller 4 to the control system 5A of the master rotorcraft 2 and the control systems 5B of the slave rotorcrafts 3, or by automatic controls based on flight programs previously stored in the control system 5A of the master rotorcraft 2 and the control systems 5B of the slave rotorcrafts 3.

FIG. 8 is a top view showing an example where the slave rotorcrafts 3 of the rotorcraft 1 shown in FIG. 1 have been connected to the master rotorcraft 2 at different positions respectively.

Although FIG. 1 shows an example in which the slave rotorcrafts 3 have been detachably coupled to the radially disposed detachable arms 11A respectively, the slave rotorcrafts 3 may be detachably coupled to the detachable arms 11A disposed in parallel, respectively, as shown in FIG. 8. As exemplified in FIG. 1 and FIG. 8, positions at which the slave rotorcrafts 3 are coupled to the master rotorcraft 2 are flexible.

Besides the above-mentioned structures, the second main rotors 3A included in the all or a part of the slave rotorcrafts 3 may be configured to be tilted relatively to the master rotorcraft 2. The second main rotor 3A of the slave rotorcraft 3 to be tilted can be tilted relatively to the slave rotorcraft 3. Alternatively, the second main rotor 3A to be tilted may be tilted, together with the slave rotorcraft 3, relatively to the master rotorcraft 2.

FIG. 9 shows an example in which each of the slave rotorcrafts 3 shown in FIG. 1 can be tilted relative to the master rotorcraft 2.

As shown in FIG. 9, at least one of the master rotorcraft 2 and the slave rotorcrafts 3 can be provided with tilt structures 60A which tilt the slave rotorcrafts 3 relatively to the master rotorcraft 2 respectively. In this case, the second main rotors 3A can be tilted relatively to the master rotorcraft 2 by tilting the slave rotorcrafts 3 themselves relatively to the master rotorcraft 2 respectively.

As a specific example, the slave rotorcraft 3 can be rotated relatively to the master rotorcraft 2 by attaching the tilt structure 60A, having a typical structure which receives a shaft with a ball bearing, to the detachable arm 11A. Alternatively, as another specific example, when the slave rotorcraft 3 has the stub wings 47A each having a tilting function by the rotation shaft 51 as exemplified in FIG. 6 and FIG. 7, the slave rotorcraft 3 can be tilted relatively to the master rotorcraft 2 by tilting the stub wing 47A which has been coupled to the detachable arm 11A of the master rotorcraft 2.

FIG. 10 shows an example in which the second main rotor 3A of each of the slave rotorcrafts 3 shown in FIG. 1 can be tilted relative to the slave rotorcraft 3.

As shown in FIG. 10, each of the slave rotorcrafts 3 may be provided with a tilt structure 60B which tilts the second main rotor 3A relative to the slave rotorcraft 3. In this case, the second main rotor 3A can be tilted relatively to the master rotorcraft 2 by tilting the second main rotor 3A relatively to the slave rotorcraft 3. Each tilt structure 60B which tilts the second main rotor 3A relatively to the slave rotorcraft 3 can also be composed of known parts, such as a ball bearing and a shaft.

Each of the tilt structure 60A and the tilt structure 60B as exemplified in FIG. 9 and FIG. 10 respectively can also be driven by remote control by an operator, by automatic control by a flight program or by a manual operation by a pilot.

(Method of Controlling Rotorcraft)

Next, a specific example of a method of controlling the rotorcraft 1 will be described.

As mentioned above, operations of the master rotorcraft 2 and the respective slave rotorcrafts 3, control for attachment and detachment between the master rotorcraft 2 and each of the slave rotorcrafts 3, charge of each slave rotorcraft 3 consisting of an electric rotorcraft, and control of the tilt structures 60A or the tilt structures 60B can be performed according to a desired algorithm, by remote control of the control system 5A and the control systems 5B of the master rotorcraft 2 and the slave rotorcrafts 3 by an operator who operates the controller 4, by automatic control according to flight programs stored in the control system 5A and the control systems 5B of the master rotorcraft 2 and the slave rotorcrafts 3, or by manual operation of the control system 5A and the control systems 5B of the master rotorcraft 2 and the slave rotorcrafts 3 by a pilot.

As a typical example, flight control and detachment control can be performed so that the master rotorcraft 2 and the slave rotorcrafts 3, which have been coupled to the master rotorcraft 2, fly to a destination, and each of the slave rotorcrafts 3 is separated from the master rotorcraft 2 at the destination. That is, after the master rotorcraft 2 arrives at a destination where a mission should be carried out, each of the slave rotorcrafts 3 can be separated from the master rotorcraft 2 so that each of the slave rotorcrafts 3 can be put into practice as the independent second rotorcraft.

In a case where each slave rotorcraft 3 is an electric rotorcraft, rotation of the second main rotor 3A and the second tail rotor 3B of each slave rotorcraft 3 can be stopped while each slave rotorcraft 3 has been coupled to the master rotorcraft 2. Thereby, an amount of consumption in electric power stored in the batteries 8 of the slave rotorcrafts 3 can be reduced. That is, an amount of consumption in electric power stored in the batteries 8 of the slave rotorcrafts 3 can be reduced by flying the slave rotorcrafts 3 only by the lift force of the master rotorcraft 2 to the destination where the slave rotorcrafts 3 are separated from the master rotorcraft 2. Meanwhile, also in a case where at least one of the slave rotorcrafts 3 has an engine, an amount of consumption in aviation fuel can be reduced.

Accordingly, the flight range and flight duration of each slave rotorcraft 3 can be increased. As a result, a mission requiring a longer time and/or a mission at a farther location can be performed. In particular, when at least one of the slave rotorcrafts 3 is an electric rotorcraft, the shortness in flight duration and radius of action, which is a weakness of an electric rotorcraft, can be remarkably improved.

Furthermore, when at least one of the slave rotorcrafts 3 is an electric rotorcraft which rotates the second main rotor 3A and the second tail rotor 3B by the motor 7 driven by the battery 8 while the master rotorcraft 2 has the engine 6 and at least one of the generator 10 and the battery charger 9, each battery 8 for rotating the second main rotor 3A and the second tail rotor 3B of the slave rotorcraft 3 can be charged by the generator 10 or the battery charger 9 mounted in the master rotorcraft 2 during a period when the slave rotorcrafts 3, each consisting of an electric rotorcraft, have been coupled to the master rotorcraft 2. In this case, the flight range and flight duration of each slave rotorcraft 3 can be increased further.

Meanwhile, also in a case where both of the slave rotorcrafts 3 and the master rotorcraft 2 are electric rotorcrafts, the batteries 8 of the slave rotorcrafts 3 can be charged by the battery charger 9 mounted in the master rotorcraft 2 while the slave rotorcrafts 3 have been coupled to the master rotorcraft 2 as long as the battery charger 9, such as a battery, mounted in the master rotorcraft 2 stores sufficient electric power. Thereby, the flight range and flight duration of each slave rotorcraft 3 can be increased further.

Even when the slave rotorcrafts 3 have been coupled to the master rotorcraft 2, at least one of the second main rotors 3A of the slave rotorcrafts 3 may be rotated under conditions where it is desired to increase the lift force of the whole rotorcraft 1 including the master rotorcraft 2 and the slave rotorcrafts 3. As a typical example, the second main rotors 3A of the slave rotorcrafts 3 which have been coupled to the master rotorcraft 2 can be rotated at the time of a strong wind.

Thus, the resistance characteristics of the rotorcraft 1 against a strong wind can be improved. That is, a flight of the rotorcraft 1 at the time of a strong wind can be permitted by improving stability of the rotorcraft 1 under the strong wind.

As another example, when the first main rotor 2A of the master rotorcraft 2 is broken down, at least one of the second main rotors 3A of the slave rotorcrafts 3 can be rotated. Thus, redundancy of the rotorcraft 1 can be secured. In other words, coupling the slave rotorcrafts 3 to the master rotorcraft 2 gives redundancy to the master rotorcraft 2.

When the slave rotorcrafts 3 have been coupled to the master rotorcraft 2, the second main rotors 3A or the slave rotorcrafts 3 may be tilted relatively to the master rotorcraft 2 and the tilted second main rotors 3A may be rotated. As a practical example, the flight speed of the rotorcraft 1 can be increased by tilting the rotating shafts of the second main rotors 3A, from the vertical direction to a traveling direction of the rotorcraft 1, and rotating the tilted second main rotors 3A, like tilt rotors, while the slave rotorcrafts 3 have been coupled to the master rotorcraft 2, as exemplified in FIG. 9 or FIG. 10.

Examples of a period when it is desired to increase the lift force of the whole rotorcraft 1 include a period when the rotorcraft 1 is taking off and a period when the rotorcraft 1 is hovering, besides a period when a strong wind is blowing. Thus, when the rotorcraft 1 is taking off or hovering, the second main rotors 3A of the slave rotorcrafts 3 can be rotated with setting the angles of the second main rotors 3A to those by which the lift force can be obtained. Meanwhile, when the rotorcraft 1 is advancing, the second main rotors 3A of the slave rotorcrafts 3 may also be rotated with tilting each of the rotating shafts of the second main rotors 3A of the slave rotorcrafts 3 in a traveling direction of the rotorcraft 1, as mentioned above. In this case, a flying speed of the rotorcraft 1 can be increased when the rotorcraft 1 is advancing while a lift force sufficient for a takeoff or hovering of the rotorcraft 1 can be obtained at the time of a takeoff or hovering of the rotorcraft 1 respectively.

On the contrary, until the slave rotorcrafts 3 are separated from the master rotorcraft 2, the second main rotors 3A of the slave rotorcrafts 3 may be stopped as long as conditions under which the lift force should be increased are not satisfied, as mentioned above. That is, the rotorcraft 1 can be designed so that a sufficient lift force can be obtained by rotation of the first main rotor 2A of the master rotorcraft 2 even when rotation of the second main rotors 3A of the slave rotorcrafts 3 is stopped, or so that a sufficient lift force can be obtained by rotation of the second main rotors 3A of the slave rotorcrafts 3 as well as rotation of the first main rotor 2A of the master rotorcraft 2.

When the rotorcraft 1 is designed so that a sufficient lift force can be obtained even when rotation of the second main rotors 3A of the slave rotorcrafts 3 is stopped, the flight duration and the flight range of each slave rotorcraft 3 can be increased as mentioned above. In addition, redundancy can be given to the rotorcraft 1. On the contrary, when the rotorcraft 1 is designed so that a sufficient lift force can be obtained by rotating the second main rotors 3A of the slave rotorcrafts 3 in addition to the first main rotor 2A of the master rotorcraft 2, the lift force required for the master rotorcraft 2 can be reduced.

EFFECTS

As described above, the rotorcraft 1 and the method of controlling the rotorcraft 1 are to enable at least one slave rotorcraft 3, each consisting of a rotorcraft which can fly independently, to attach and detach to and from the master rotorcraft 2 consisting of another rotorcraft which can fly independently.

According to the rotorcraft 1 and the method of controlling the rotorcraft 1, the rotorcraft 1 can fly from a takeoff point to a targeted area, in the form of a single rotorcraft, for a mission requiring simultaneous operations by a plurality of rotorcrafts. On the contrary, the plurality of the rotorcrafts including the master rotorcraft 2 and the slave rotorcrafts 3 can return in the form of the single rotorcraft 1 after the mission has been completed. As a result, maneuvering the plurality of the rotorcrafts including the master rotorcraft 2 and the slave rotorcrafts 3 can be made easy.

In particular, when at least one slave rotorcrafts 3 is an electric rotorcraft, the flight range and flight duration of the slave rotorcraft 3 can be lengthened by coupling the slave rotorcraft 3 to the master rotorcraft 2. Moreover, when at least one of the generator 10 and the battery charger 9 is mounted in the master rotorcraft 2, each electric slave rotorcraft 3 coupled to the master rotorcraft 2 can be charged. As a result, the flight range and flight duration of each slave rotorcraft 3 can be lengthened further.

(Other Implementations)

While certain implementations have been described, these implementations have been presented by way of example only, and are not intended to limit the scope of the invention. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention. 

What is claimed is:
 1. A rotorcraft comprising: a first rotorcraft having a first main rotor and a first tail rotor; and at least one second rotorcraft having a second main rotor and a second tail rotor, the at least one second rotorcraft being attachable and detachable to and from the first rotorcraft.
 2. The rotorcraft according to claim 1, wherein the first main rotor rotates by an engine, and the second main rotor rotates electrically.
 3. The rotorcraft according to claim 1, wherein the first rotorcraft has at least one of a charger and a generator which charges a battery, for rotating the second main rotor, the battery being charged in a state where the at least one second rotorcraft has been attached to the first rotorcraft.
 4. The rotorcraft according to claim 1, wherein at least one of the first rotorcraft and the at least one second rotorcraft has a tilt structure, having a shaft and a ball bearing receiving the shaft, that tilts the second main rotor relative to the at least one second rotorcraft or tilts the at least one second rotorcraft relative to the first rotorcraft.
 5. The rotorcraft according to claim 1, wherein both the first rotorcraft and the at least one second rotorcraft are unmanned aircrafts.
 6. A method of controlling the rotorcraft according to claim 1, comprising: flying the first rotorcraft, to which the at least one second rotorcraft has been attached, to a destination; and separating the at least one second rotorcraft from the first rotorcraft at the destination.
 7. The method according to claim 6, wherein the second main rotor is stopped until the at least one second rotorcraft is separated from the first rotorcraft, unless a condition, under which a lift force should be increased, has been satisfied.
 8. The method according to claim 6, wherein the second main rotor of the at least one second rotorcraft which has been attached to the first rotorcraft is rotated when a wind is strong.
 9. The method of according to claim 6, wherein the second main rotor of the at least one second rotorcraft is rotated when the first main rotor is broken down.
 10. The method according to claim 6, wherein a battery for rotating the second main rotor is charged by a generator or a charger mounted in the first rotorcraft, during a period when the at least one second rotorcraft has been attached to the first rotorcraft.
 11. The method of controlling the rotorcraft according to claim 4, wherein a flight speed is increased by tilting the second main rotor or the at least one second rotorcraft and rotating the second main rotor, during a period when the at least one second rotorcraft has been attached to the first rotorcraft. 